Cell-specific reference signal (crs) and control channel configuration in wireless communications

ABSTRACT

Efficient cell-specific reference signal (CRS) and control channel configurations may be established dynamically based on channel conditions for one or more user equipment (UE) that may be served by a transmission. A base station may configure a CRS for a transmission time interval (TTI) based at least in part on a channel quality of one or more UEs that are to receive transmissions during the TTI. A number of downlink symbols at the beginning of the TTI may be used for CRS transmissions, and UEs with better channel quality may receive CRS transmissions and other control information in a first symbol, while UEs with a poorer channel quality may receive higher power CRS transmissions in the first symbol and the other control information is transmitted in a subsequent symbol.

CROSS REFERENCES

The present application for patent claims priority to U.S. ProvisionalPatent Application No. 62/384,689 by Yoo, et al., entitled“Cell-Specification Reference Signal (CRS) And Control ChannelConfiguration In Wireless Communications,” filed Sep. 7, 2016, assignedto the assignee hereof.

INTRODUCTION

The following relates generally to wireless communication, and morespecifically to cell-specific reference signal (CRS) and control channelconfiguration in wireless communications.

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing the available system resources (e.g., time, frequency, andpower). Examples of such multiple-access systems include code-divisionmultiple access (CDMA) systems, time-division multiple access (TDMA)systems, frequency-division multiple access (FDMA) systems, andorthogonal frequency-division multiple access (OFDMA) systems.

In some examples, a wireless multiple-access communication system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple communication devices, otherwise known asuser equipment (UEs). In a Long-Term Evolution (LTE) or LTE-Advanced(LTE-A) network, a set of one or more base stations may define an eNodeB(eNB). In other examples (e.g., in a next generation or 5G network), awireless multiple access communication system may include a number ofnext generation NodeBs (gNBs) which in some cases may include smartradio heads (radio heads (RHs)) in communication with a number of accessnode controllers (ANCs). A base station may communicate with a set ofUEs on downlink (DL) channels (e.g., for transmissions from a basestation to a UE) and uplink (UL) channels (e.g., for transmissions froma UE to a base station).

Subframes of communication between a network access device (e.g., a gNB,an eNB, an ANC, a RH, or a base station) and a plurality of UEs mayinclude different regions or channels that are assembled in accordancewith a time division duplex (TDD) and/or frequency division duplex (FDD)subframe structure. Subframes may also include arrangements of ULchannels and/or DL channels. Subframes may also include one or morereference signals that may be used for control channel demodulation. Incases where wireless transmissions may use shared radio frequencyspectrum, reference signals may also be used to detect whether atransmitter is transmitting, and/or one or more channels used for atransmission. Providing such reference signals that can provide reliableand efficient use of system resources may enhance the operation of awireless multiple-access communication system.

SUMMARY

A method of wireless communication is described. The method may includeidentifying at least a first UE that is to receive a downlinktransmission during a first transmission time interval (TTI),identifying a channel quality of the first UE, configuring acell-specific reference signal (CRS) based at least in part on thechannel quality of the first UE, and transmitting the CRS to the firstUE during the first TTI.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying at least a first UE that is to receive adownlink transmission during a first TTI, means for identifying achannel quality of the first UE, means for configuring a CRS based atleast in part on the channel quality of the first UE, and means fortransmitting the CRS to the first UE during the first TTI.

Another apparatus for wireless communication is described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to identify at least a first UE thatis to receive a downlink transmission during a first TTI, identify achannel quality of the first UE, configure a CRS based at least in parton the channel quality of the first UE, and transmit the CRS to thefirst UE during the first TTI.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions operable to cause a processor to identify at least a firstUE that is to receive a downlink transmission during a first TTI,identify a channel quality of the first UE, configure a CRS based atleast in part on the channel quality of the first UE, and transmit theCRS to the first UE during the first TTI.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for configuring a starting point for adownlink control channel transmission to the first UE within the TTIbased at least in part on the CRS. Some examples of the method,apparatus, and non-transitory computer-readable medium described abovemay configure a CRS transmission power based at least in part on thechannel quality of the first UE, and may configure a concurrent downlinkcontrol channel transmission power based at least in part on the CRStransmission power.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for dynamically configuring the CRS foreach TTI of a plurality of TTIs based at least in part on the channelquality of one or more UEs to receive the downlink transmission duringthe TTI.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying a second set of UEsthat are to receive a second downlink transmission during a second TTI,identifying a second UE of the second set of UEs having a poorer channelquality than other UEs of the second set of UEs; configuring a secondCRS based at least in part on the channel quality of the second UE; andtransmitting the second CRS to the second set of UEs during the secondTTI.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, a first symbol of the TTIcomprises a set of resource elements (REs), and wherein the configuringthe CRS comprises: configuring a first subset of the REs fortransmission of the CRS, configuring a second subset of the REs for adownlink control channel transmission, configuring a first power for thefirst subset of REs based at least in part on the channel quality of thefirst UE, and configuring a second power for the second subset of REsbased at least in part on the first power.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, a second symbol of the TTIcomprises a physical downlink control channel (PDCCH) transmission. Someexamples of the method, apparatus, and non-transitory computer-readablemedium described above may further include processes, features, means,or instructions for transmitting signaling to the first UE thatindicates whether the PDCCH transmission starts in the first symbol orin the second symbol. Signaling may include, in some examples, layer-one(L1) signaling transmitted in the first symbol or a search spacerestriction for the first UE.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the first power for the firstsubset of REs may be configured with a higher power than the secondpower for the second subset of REs when the channel quality of the firstUE is below a threshold value. In some examples of the method,apparatus, and non-transitory computer-readable medium described above,the downlink control channel transmission may be deferred to a secondsymbol of the TTI after the first symbol when the second power for thesecond subset of REs is below the power threshold value. In someexamples, the first power for the first subset of REs may be configuredwith equivalent power as the second power for the second subset of REswhen the channel quality of the first UE is above a threshold value.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, each of a first symbol of theTTI and a second symbol of the TTI comprise a set of REs, and whereinthe configuring the CRS comprises: configuring a first subset of the REsacross the first symbol and second symbol for transmission of the CRS,and configuring a second subset of the REs in each of the first symboland second symbol for transmission of a downlink control channeltransmission. Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for transmitting signaling to the firstUE that the first UE is to receive the CRS transmitted in the firstsymbol or that the first UE is to combine the CRS transmissions from thefirst symbol and the second symbol, based at least in part on thechannel quality of the UE. In some examples, the signaling to the firstUE may indicate whether only a first symbol of the TTI or both the firstsymbol and a second symbol of the TTI include CRS and downlink controlinformation, and, when both the first symbol and the second symbolinclude CRS and downlink control information, whether the second symbolincludes CRS transmissions. In some examples, the signaling may be L1signaling transmitted in the first symbol of the TTI.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the configuring the CRSfurther comprises determining whether the channel quality of the firstUE exceeds a threshold value, configuring a concurrent downlink controlchannel transmission in a second subset of resources of the first symbolwhen the channel quality of the first UE exceeds the threshold value,and configuring a second CRS for transmission in the second subset ofresources of the first symbol when the channel quality of the first UEdoes not exceed the threshold value.

A method of wireless communication is described. The method may includereceiving, at a UE, a downlink transmission from a base station during afirst TTI, determining a CRS configuration of the downlink transmission,and receiving the CRS based at least in part on the CRS configuration.

An apparatus for wireless communication is described. The apparatus mayinclude means for receiving, at a UE, a downlink transmission from abase station during a first TTI, means for determining a CRSconfiguration of the downlink transmission, and means for receiving theCRS based at least in part on the CRS configuration.

Another apparatus for wireless communication is described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to receive, at a UE, a downlinktransmission from a base station during a first TTI, determine a CRSconfiguration of the downlink transmission, and receive the CRS based atleast in part on the CRS configuration.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions operable to cause a processor to receive, at a UE, adownlink transmission from a base station during a first TTI, determinea CRS configuration of the downlink transmission, and receive the CRSbased at least in part on the CRS configuration.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for determining a starting point for adownlink control channel transmission within the TTI based at least inpart on the CRS configuration. Some examples of the method, apparatus,and non-transitory computer-readable medium described above may furtherinclude processes, features, means, or instructions for receivingsignaling that indicates a starting point for a PDCCH based at least inpart on the CRS configuration. In some examples, the signaling comprisesL1 signaling transmitted in a first symbol of the TTI or a search spacerestriction for the first UE.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, each of a first symbol of theTTI and a second symbol of the TTI comprise a portion of the CRStransmission, and wherein the receiving the CRS comprises: combining CRStransmissions received in the first symbol and second symbol. Someexamples of the method, apparatus, and non-transitory computer-readablemedium described above may further include processes, features, means,or instructions for receiving signaling that the CRS transmissions fromthe first symbol and the second symbol are to be combined.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving signaling from the basestation that indicates whether only a first symbol of the TTI or boththe first symbol and a second symbol of the TTI include CRS and downlinkcontrol information, and, when both the first symbol and the secondsymbol include CRS and downlink control information, whether the secondsymbol includes CRS transmissions. In some examples, the signaling maybe layer-one (L1) signaling transmitted in the first symbol of the TTI.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the determining the CRSconfiguration comprises determining that a first CRS is configured fortransmission in a first subset of resources of a first symbol of theTTI. Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for determining whether a concurrentdownlink control channel transmission is configured in a second subsetof resources of the first symbol, or a second CRS is configured fortransmission in the second subset of resources of the first symbol. Someexamples of the method, apparatus, and non-transitory computer-readablemedium described above may further include processes, features, means,or instructions for blindly detecting the presence of the second CRS.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentdisclosure may be realized by reference to the following drawings. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 illustrates an example of a system for wireless communicationthat supports cell-specific reference signal (CRS) and control channelconfiguration in wireless communications in accordance with aspects ofthe present disclosure.

FIG. 2 illustrates an example of a wireless communications system thatsupports CRS and control channel configuration in wirelesscommunications in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a CRS and control channel configurationin accordance with aspects of the present disclosure.

FIG. 4 illustrates another example of a CRS and control channelconfiguration in accordance with aspects of the present disclosure.

FIG. 5 illustrates another example of a CRS and control channelconfiguration in accordance with aspects of the present disclosure.

FIG. 6 illustrates another example of a CRS and control channelconfiguration in accordance with aspects of the present disclosure.

FIG. 7 illustrates another example of a CRS and control channelconfiguration in accordance with aspects of the present disclosure.

FIGS. 8 through 10 show block diagrams of a device that supports CRS andcontrol channel configuration in wireless communications in accordancewith aspects of the present disclosure.

FIG. 11 illustrates a block diagram of a system including a base stationthat supports CRS and control channel configuration in wirelesscommunications in accordance with aspects of the present disclosure.

FIGS. 12 through 14 show block diagrams of a device that supports CRSand control channel configuration in wireless communications inaccordance with aspects of the present disclosure.

FIG. 15 illustrates a block diagram of a system including a UE thatsupports CRS and control channel configuration in wirelesscommunications in accordance with aspects of the present disclosure.

FIGS. 16 through 20 illustrate methods for CRS and control channelconfiguration in wireless communications in accordance with aspects ofthe present disclosure.

DETAILED DESCRIPTION

Techniques are described that provide efficient CRS and control channelconfigurations that may be established dynamically based on channelconditions for one or more user equipment (UE) that may be served by atransmission. Next generation networks (e.g., 5G or new radio (NR)networks) are being designed to support features such as high bandwidthoperations, more dynamic subframe types, and self-contained subframetypes (in which hybrid automatic repeat request (HARD) feedback for asubframe may be transmitted before the end of the subframe). Further,some networks may utilize radio frequency spectrum in which particularCRS and control channel configurations may help to provide efficientsignaling to one or more UEs. For example, some networks may use sharedradio frequency spectrum in which CRS transmissions may be used to helpdetect transmissions, or beamforming of CRS transmissions may be used inmillimeter wave deployments or deployments that use coordinatedmulti-point (CoMP) transmissions.

According to various aspects of the disclosure, a base station mayconfigure a CRS for a transmission time interval (TTI) based at least inpart on a channel quality of one or more UEs that are to receivetransmissions during the TTI. In some cases, a number of downlinksymbols at the beginning of the TTI may be used for CRS transmissions,and UEs with better channel quality (e.g., UEs near a center of acoverage area of a base station) may receive CRS transmissions and othercontrol information in a first symbol, while UEs with a poorer channelquality (e.g., UEs near an edge of a coverage area of a base station)may receive higher power CRS transmissions in the first symbol and theother control information in a subsequent symbol. In some examples, theconfiguration of the CRS and control information within one or moresymbols may be dynamically configured based on the conditions of UEsthat are to receive the transmission. In some examples, a base stationmay frequency division multiplex (FDM) CRS and control information in afirst symbol of a TTI when the UE that is to receive the transmissionhas a relatively good channel quality. The base station, in someexamples, may increase a transmission power for CRS tones and decreasetransmission power for control tones based at least in part on a channelquality metric (e.g., CQI) of the receiving UE.

While various examples described herein refer to a base stationidentifying CRS and control channel configurations based on a single UE,it will be understood that CRS may be common to multiple UEs beingserved during a TTI by a base station, and a base station may serve amix of UEs with both relatively good and relatively poor channelqualities in one TTI. In such a case, the base station may use the CRSand control channel configuration for UEs with relatively poor channelqualities to make sure that the CRS and control can reliably reach allthe UEs. In such cases, the UEs with relatively good channel qualitywill see CRS and control channel configuration that are established forthe UEs with relatively poor channel qualities. In cases where a basestation is exclusively serving one or more UEs with relatively goodchannel quality in a TTI, each UE will see the CRS and controlconfiguration that are established for the UEs with relatively goodchannel qualities. Thus, in examples that describe the determination ofa CRS and control channel configuration for only a single UE, such aconfiguration may apply to one or more other UEs being served in thesame TTI that have better channel qualities. It is to be noted, however,that in examples that utilize millimeter wave or CoMP transmissiontechniques, as will be discussed below, CRS and control channelconfiguration may be selected individually for each UE.

A UE operating in systems that provide CRS and control channelconfiguration according to various aspects of the disclosure may receivea downlink transmission from a base station, determine the CRSconfiguration of the downlink transmission, and receive the CRS based atleast in part on the determined CRS configuration. In some cases, a UEmay determine a CRS configuration based on signaling from the basestation (e.g., layer-one (L1) signaling or a search space restrictionprovided to the UE) that indicates the CRS configuration.

Aspects of the disclosure are initially described in the context of awireless communications system. Aspects of the disclosure are furtherillustrated by and described with reference to apparatus diagrams,system diagrams, and flowcharts that relate to CRS and control channelconfiguration in wireless communications.

FIG. 1 illustrates an example of a wireless communication system 100, inaccordance with various aspects of the disclosure. The wirelesscommunication system 100 may include base stations 105 (e.g., gNodeBs(gNBs), network access devices, access node controllers (ANCs) and/orradio heads (RHs)), UEs 115, and a core network 130. Wirelesscommunication system 100 may support dynamic CRS and control channelconfiguration for transmissions in different TTIs, based on one or moreconditions at a receiving UE.

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. At least some of the basestations 105 (e.g., network access devices, gNBs, ANCs, RHs) mayinterface with the core network 130 through backhaul links 132 (e.g.,S1, S2, etc.) with the core network 130 and may perform radioconfiguration and scheduling for communication with the UEs 115. Invarious examples, ANCs may communicate, either directly or indirectly(e.g., through core network 130), with each other over backhaul links134 (e.g., X1, X2, etc.), which may be wired or wireless communicationlinks. Each ANC may additionally or alternatively communicate with anumber of UEs 115 through a number of smart radio heads. In analternative configuration of the wireless communication system 100, thefunctionality of an ANC may be provided by a radio head or distributedacross the radio heads of a gNB.

In some examples, the wireless communication system 100 may include a 5Gnetwork. In other examples, the wireless communication system 100 mayinclude a LTE/LTE-A network. The wireless communication system 100 mayin some cases be a heterogeneous network, in which different types ofbase stations 105 (e.g., gNBs, eNBs, ANCs, etc.) provide coverage forvarious geographical regions. The term “cell” is a 3GPP term that can beused to describe a base station, a radio head, a carrier or componentcarrier associated with a base station or a radio head, or a coveragearea (e.g., sector, etc.) of a carrier or base station, depending oncontext.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude uplink transmissions from a UE 115 to a base station 105, ordownlink transmissions, from a base station 105 to a UE 115. A UE 115may communicate with the core network 130 through communication link135. UEs 115 may be dispersed throughout the wireless communicationssystem 100, and each UE 115 may be stationary or mobile.

The communication networks that may accommodate some of the variousdisclosed examples may be packet-based networks that operate accordingto a layered protocol stack. In the user plane, communications at thebearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based.A Radio Link Control (RLC) layer may in some cases perform packetsegmentation and reassembly to communicate over logical channels. AMedium Access Control (MAC) layer may perform priority handling andmultiplexing of logical channels into transport channels. The MAC layermay also use Hybrid ARQ (HARD) to provide retransmission at the MAClayer to improve link efficiency. In the control plane, the RadioResource Control (RRC) protocol layer may provide establishment,configuration, and maintenance of an RRC connection between a UE 115 anda base station 105, or core network 130 supporting radio bearers foruser plane data. At the Physical (PHY) layer, transport channels may bemapped to physical channels.

The UEs 115 may be dispersed throughout the wireless communicationsystem 100, and each UE 115 may be stationary or mobile. A UE 115 mayadditionally or alternatively be referred to as a mobile station, asubscriber station, a mobile unit, a subscriber unit, a wireless unit, aremote unit, a mobile device, a wireless device, a wirelesscommunications device, a remote device, a mobile subscriber station, anaccess terminal, a mobile terminal, a wireless terminal, a remoteterminal, a handset, a user agent, a mobile client, a client, or someother suitable terminology. A UE 115 may additionally or alternativelybe a cellular phone, a personal digital assistant (PDA), a wirelessmodem, a wireless communication device, a handheld device, a tabletcomputer, a laptop computer, a cordless phone, a wireless local loop(WLL) station, an Internet of things (IoT) device, an Internet ofEverything (IoE) device, a machine type communication (MTC) device, anappliance, an automobile, or the like.

The communication links 125 shown in wireless communication system 100may include uplink channels from a UE 115 to a base station 105, and/ordownlink channels, from a base station 105 to a UE 115. The downlinkchannels may also be called forward link channels, while the uplinkchannels may also be called reverse link channels. Control informationand data may be multiplexed on an uplink channel or downlink accordingto various techniques. Control information and data may be multiplexedon a downlink channel, for example, using TDM techniques, FDMtechniques, or hybrid TDM-FDM techniques. In some examples, the controlinformation transmitted during a TTI of a downlink channel may bedistributed between different control regions in a cascaded manner(e.g., between a common control region and one or more UE-specificcontrol regions).

One or more of base stations 105 may include a network communicationmanager 101, which may identify a UE 115 that is to receive a downlinktransmission during a first TTI, identify a channel quality of the UE115 (e.g., based on a channel quality indicator (CQI) provided by the UE115, a sounding reference signal (SRS) received from the UE 115, areceived signal reference power (RSRP) of the UE 115, a reference signalreceived quality (RSRQ) of the UE 115, or any combination thereof), andconfigure a CRS transmission based at least in part on the channelquality of the UE 115. Control information may be configured to betransmitted concurrently with CRS within a same symbol in cases wherethe channel quality is relatively good, and may be configured to betransmitted after the CRS when channel quality is relatively poor, forexample.

UEs 115 may include a UE communication manager 102, which may receive adownlink transmission from a base station 105 during a TTI, determine aCRS configuration of the downlink transmission, and receive the CRSbased at least in part on the CRS configuration. In examples that useshared spectrum for transmissions, the CRS may be used to determinewhether a base station 105 is transmitting in a TTI (e.g., whether thebase station successfully completed a listen before talk (LBT)procedure), and/or a number of channels that may be used in atransmission (e.g., a number of 20 MHz channels of a 80 MHz systembandwidth that passed LBT).

Wireless communication system 100 may support operation on multiplecells or carriers, a feature which may be referred to as carrieraggregation (CA) or multi-carrier operation. A carrier may also bereferred to as a component carrier (CC), a layer, a channel, etc. Theterms “carrier,” “component carrier,” “cell,” and “channel” may be usedinterchangeably herein. A UE 115 may be configured with multipledownlink CCs and one or more uplink CCs for carrier aggregation. Carrieraggregation may be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including: wider bandwidth, shorter symbol duration, andshorter transmission time interval (TTIs). In some cases, an eCC may beassociated with a carrier aggregation configuration or a dualconnectivity configuration (e.g., when multiple serving cells have asuboptimal or non-ideal backhaul link). An eCC may also be configuredfor use in unlicensed spectrum or shared spectrum (where more than oneoperator is allowed to use the spectrum).

In some cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration isassociated with increased subcarrier spacing. A device, such as a UE 115or base station 105, utilizing eCCs may transmit wideband signals (e.g.,20, 40, 60, 80 Mhz, etc.) at reduced symbol durations (e.g., 16.67microseconds). A TTI in eCC may consist of one or multiple symbols. Insome cases, the TTI duration (that is, the number of symbols in a TTI)may be variable. A 5G new radio (NR) carrier may be considered an eCC.

Downlink control information may be transmitted from a base station 105to a UE 115 using one or more physical downlink control channel (PDCCH)transmissions. In some examples, PDCCH transmissions may be transmittedconcurrently with CRS transmissions, or may be transmitted following CRStransmissions within a TTI. The PDCCH may carry a message known asdownlink control information (DCI), which includes transmission resourceassignments and other control information for a UE 115 or group of UEs115, such as downlink scheduling assignments, uplink resource grants,transmission scheme, uplink power control, hybrid automatic repeatrequest (HARD) information, MCS and other information, or anycombinations thereof. To reduce power consumption and overhead at the UE115, a limited set of transmission resources may be specified for DCIassociated with a specific UE 115, which may be known as a search space.The search space can be partitioned into two regions: a search space anda UE-specific (dedicated) search space.

Wireless communication system 100 may operate in an ultra high frequency(UHF) frequency region using frequency bands from 700 MHz to 2600 MHz(2.6 GHz), although in some cases wireless local area network (WLAN)networks may use frequencies as high as 4 GHz. This region may also beknown as the decimeter band, since the wavelengths range fromapproximately one decimeter to one meter in length. UHF waves maypropagate mainly by line of sight, and may be blocked by buildings andenvironmental features. However, the waves may penetrate wallssufficiently to provide service to UEs 115 located indoors. Transmissionof UHF waves is characterized by smaller antennas and shorter range(e.g., less than 100 km) compared to transmission using the smallerfrequencies (and longer waves) of the high frequency (HF) or very highfrequency (VHF) portion of the spectrum. In some cases, wirelesscommunication system 100 may also utilize extremely high frequency (EHF)portions of the spectrum (e.g., from 30 GHz to 300 GHz). This region mayalso be known as the millimeter band, since the wavelengths range fromapproximately one millimeter to one centimeter in length, and systemsthat use this region may be referred to as millimeter wave (mmWave)systems. Thus, EHF antennas may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115 (e.g., for directional beamforming). However, EHFtransmissions may be subject to even greater atmospheric attenuation andshorter range than UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions.

FIG. 2 illustrates an example of a wireless communications system 200that supports CRS and control channel configuration in wirelesscommunications in accordance with aspects of the present disclosure.Wireless communications system 200 may include base station 105-d, andUE 115-a, which may be examples of the corresponding devices describedwith reference to FIG. 1. Wireless communications system 200 may use acommunications configuration that includes uplink-centric subframes anddownlink-centric subframes that may include CRS and control informationin one or more initial symbols of a subframe transmitted in a downlinktransmission 210.

CRS transmissions in downlink transmission 210 may be used, for example,to aid in control channel demodulation at the UE 115-a. In exampleswhere the downlink transmission is made using shared spectrum, whetherthe downlink transmission 210 is transmitted at all depends upon theoutcome of an LBT procedure. In such cases, the CRS may be used forburst detection to determine if the base station 105-d is transmittingat a given subframe on a given channel. Furthermore, CRS may be used forbandwidth detection. For example, certain deployments may use sharedspectrum in which LBT procedures are performed individually for multiplechannels of a total system bandwidth (e.g., LBT may be performed per 20MHz channel of an 80 MHz system bandwidth). In such deployments, the UE115-a may perform burst detection for each channel of the systembandwidth, in order to figure out the actual transmission bandwidth. Insuch shared spectrum deployments, reliable burst detection is importantand may be an important factor in the overhead required for CRS.

CRS overhead may be selected to be large in order to provide reliableburst when the UE 115-a is located at a cell edge, or edge of a coveragearea, of base station 105-d. However, if the UE 115-a is located nearthe cell center, a CRS transmission may be relatively easily detected,and a large CRS overhead may be inefficient in such situations. Ratherthan used a fixed large CRS overhead, various aspects of this disclosureprovide for dynamic CRS and control channel configurations depending onchannel conditions of the UE 115-a. Thus, the CRS resources and controlregion of downlink transmission 210 can be made dynamic (e.g., a PDCCHstarting point can be made dynamic).

In some examples, the base station 105-d may include a base stationcommunication manager 201, which may be an example of networkcommunication manager 101 of FIG. 1, and may be used to identify the UE115-a that is to receive downlink transmission 210, identify a channelquality of the UE 115-a (e.g., based on a channel quality indicator(CQI) provided by the UE 115-d), and configure a CRS transmission basedat least in part on the channel quality of the UE 115-d. Controlinformation may be configured to be transmitted concurrently with CRSwithin a same symbol in cases where the channel quality is relativelygood, and may be configured to be transmitted after the CRS when channelquality is relatively poor, for example. In some cases, the CRS may bedynamically configured for each TTI of a number of TTIs based at leastin part on the channel quality of one or more UEs 115 to receive thedownlink transmission during the TTI.

The UE 115-a may include a UE communication manager 202, which may be anexample of UE communication manager 102 of FIG. 1, and may be used toreceive downlink transmission 210 from the base station 105-d, determinea CRS configuration of the downlink transmission 210, and receive theCRS based at least in part on the CRS configuration. In examples thatuse shared spectrum for transmissions, the CRS may be used to determinewhether the base station 105-d is transmitting in a TTI (e.g., whetherthe base station 105-d successfully completed a LBT procedure), and/or anumber of channels that may be used in a transmission (e.g., a number of20 MHz channels of a 80 MHz system bandwidth that passed LBT).

FIG. 3 illustrates an example of a subframe associated with a DL-centricdynamic subframe 300 in accordance with aspects of the presentdisclosure. In some examples, the DL-centric dynamic subframe type maybe selected for the subframe 300, by a network access device such as abase station 105 of FIGS. 1-2, based at least in part on a UL/DL trafficratio. For example, a base station may select a DL-centric dynamicsubframe type for the subframe 300 when the UL/DL traffic ratio thatindicates more traffic is queued by the base station for transmission toone or more UEs than is queued by the one or more UEs for transmissionto the base station. In some examples, the base stations and UEs thatcommunicate in the subframe 300 may be examples of aspects of the basestations 105 and UEs 115 described with reference to FIGS. 1-2. Whilevarious examples described herein use downlink-centric subframes, itwill be understood that the techniques described are equally applicableto other types of subframes, such as pure downlink subframes,uplink-centric subframes that may include an initial downlinktransmission followed by uplink transmissions, or other types ofsubframes or transmissions that may use downlink CRS information.

The subframe 300 may begin with a DL control region that may include CRS305 and PDCCH 310 in an initial two symbols of the subframe 300.Following the PDCCH 310, the base station may schedule a data region315, which may include physical downlink shared channel (PDSCH)transmissions. Following the data region 315, a guard period 320 may beprovided to allow the UE to perform RF switching from downlinkreceptions to uplink transmissions. Following the guard period 320, anuplink common burst symbol 325 may be scheduled for transmission by theUE of information such as a sounding reference signal (SRS), schedulingrequest (SR), feedback (e.g., ACK/NACK information), or uplink data.Such an uplink common burst symbol 325 may allow for a self-containedsubframe 300, in which feedback on successful reception of data in thedata region 315 may be provided within the same subframe, which mayprovide for lower latency and enhanced data throughput relative toproviding feedback information in some number of subframes after thedata region 315.

As indicated above, various aspects of the disclosure provide fordynamic CRS configuration. FIG. 4 illustrates an example of a CRS andcontrol channel configuration 400 in accordance with aspects of thepresent disclosure. In some examples, a subframe 405 may have a CRS andcontrol channel configuration that is selected by a network accessdevice such as a base station 105 of FIGS. 1-2, for transmission to a UEsuch as a UE 115 of FIGS. 1-2.

The subframe 405 of this example, may span a number of symbols 410 andbe transmitted using a number of sub-carriers 415. Within a first symbolof the subframe, CRS transmissions 420 and control channel transmissions425 may be concurrently transmitted using FDM. A demodulation referencesignal (DMRS) 430 may be transmitted following the CRS 420 and controlchannel 425 transmissions, followed by downlink data such as PDSCHtransmissions 435. In this example, within the first symbol of thesubframe 405 the CRS 420 occupies one-half of the symbol (e.g., everyother frequency tone), with the remaining portion of the symbol used forcontrol transmissions 425, such as L1 control channels (e.g. physicalcontrol format indicator channel (PCFICH), physical frame formatindicator channel (PFFICH)), and PDCCH if sufficient resources areavailable. The second symbol of the subframe 405 may include controlinformation 425 such as PDCCH transmissions. The power level for the CRStransmissions 420 and control transmissions 425 may be selected based onthe channel conditions of a UE that is to receive the subframe 405.

In examples where a cell edge UE is to receive the subframe 405 and hasa relatively poor channel quality, the CRS transmissions 420 in thefirst symbol may be power-boosted to assure reliable coverage for burstdetection and control demodulation at the UE. In some cases, the amountof the power boost provided to the CRS transmissions 420 may be selectedbased on the channel quality of the UE, with a larger amount of boostprovided to UEs with poorer channel conditions. In the event that thepower boost to the CRS transmissions 420 reaches a maximum level, noadditional power may be available for control transmissions 425 in thefirst symbol, and there is no PDCCH transmission in the first symbol. Insome cases, some power may be reserved in the first symbol fortransmissions of the L1 control channels, such that the L1 controlchannels of the control transmissions 425 and the CRS transmissions 420may be transmitted, but no PDCCH transmissions may be transmitted inthis first symbol.

In examples where a cell center UE is to receive the subframe 405 andhas a relatively good channel quality, the CRS transmissions 420 in thefirst symbol may not be power-boosted, and PDCCH may be transmitted incontrol transmissions 425 of the first symbol. Accordingly, such aconfiguration technique may provide a configurable PDCCH starting symbollocation, in which PDCCH starts from the first symbol for a cell centerUE and starts from the second symbol for a cell edge UE. A particularconfiguration that is used by a base station may be signaled to the UEin a UE-specific manner, such as through L1 signaling or a search spacerestriction for the UE.

FIG. 5 illustrates an example of another a CRS and control channelconfiguration 500 in accordance with aspects of the present disclosure.In some examples, a subframe 505 may have a CRS and control channelconfiguration that is selected by a network access device such as a basestation 105 of FIGS. 1-2, for transmission to a UE such as a UE 115 ofFIGS. 1-2.

The subframe 505 of this example, similarly as discussed above, may spana number of symbols 510 and be transmitted using a number ofsub-carriers 515. Within both a first symbol of the subframe 505 and asecond symbol of the subframe 505, CRS transmissions 520 and controlchannel transmissions 525 may be concurrently transmitted using FDM. ADMRS 530 may be transmitted following the CRS 520 and control channel525 transmissions, followed by downlink data such as PDSCH transmissions535. In this example, within the first and second symbols of thesubframe 505 the CRS 520 occupies one-half of the symbol (e.g., everyother frequency tone), with the remaining portion of the symbol used forcontrol transmissions 525, such as L1 control channels (e.g. PCFICH,PFFICH), and PDCCH.

In this example, power boosting of the CRS transmissions 520 may not beprovided, and cell edge UEs may be allowed to combine CRS over the twosymbols for reliable coverage and burst detection. Cell center UEs insuch examples may rely on one symbol CRS. In some cases, the first andsecond symbols may be beamformed differently to target different UEs orsets of UEs. For example, in mmWave systems or systems that use CoMPwith UEs specifically beamformed, CRS may be beamformed to provideenhanced reception at the UE(s). Combining CRS from both the first andsecond symbols may impact a UE processing timeline associated with thesubframe 505, and in some examples a base station pay provide signalingthat indicates whether the UE should combine CRS across two symbols oruse one symbol CRS.

In other examples, a L1 signal in control transmissions 525 of the firstsymbol (e.g. PCFICH) may indicate a number of control symbols. Forexample, either one or both of the first two symbols of subframe 505 maybe used for CRS transmissions 520 and control transmissions 525. If onlya single symbol is used, the DMRS transmissions 530 and PDSCHtransmissions 535 may start at the second symbol. If both the firstsymbol and the second symbol are used for CRS transmissions 520 andcontrol transmissions 525, signaling may be provided to indicate whetherCRS transmissions 520 are present on the second symbol and should becombined with first symbol CRS transmissions 520.

FIG. 6 illustrates an example of a CRS and control channel configuration600 in accordance with aspects of the present disclosure, in which onlya single symbol is used for CRS and control transmissions. Similarly asdiscussed above, a subframe 605 may have a CRS and control channelconfiguration that is selected by a network access device such as a basestation 105 of FIGS. 1-2, for transmission to a UE such as a UE 115 ofFIGS. 1-2.

The subframe 605 of this example may span a number of symbols 610 and betransmitted using a number of sub-carriers 615. In this example, a firstsymbol of the subframe 605 may include CRS transmissions 620 and controlchannel transmissions 625 concurrently transmitted using FDM. A DMRS 630may be transmitted starting in the second symbol, followed by downlinkdata such as PDSCH transmissions 635. As indicated above, in such anexample, an L1 signal within control transmissions 625 (e.g., PCFICH)can indicate the number of control symbols (one in this case), which aUE may use to determine that both CRS transmissions 620 and controltransmissions 625, which include PDCCH, are located in the first symbol,and that DMRS/PDSCH start at the second symbol. If the L1 signalingindicates that two symbols are used for CRS transmissions 620 andcontrol transmissions 625, than a configuration such as illustrated inFIG. 4 (e.g., if PCFICH on the first symbol indicates two controlsymbols and no CRS in the second symbol) or FIG. 5 (e.g., if PCFICH onthe first symbol indicates two control symbols and CRS is in the secondsymbol) may be used.

FIG. 7 illustrates an example of another a CRS and control channelconfiguration 700 in accordance with aspects of the present disclosure.In some examples, similarly as above, a subframe 705 may have a CRS andcontrol channel configuration that is selected by a network accessdevice such as a base station 105 of FIGS. 1-2, for transmission to a UEsuch as a UE 115 of FIGS. 1-2.

The subframe 705 of this example, similarly as discussed above, may spana number of symbols 710 and be transmitted using a number ofsub-carriers 715. Within both a first symbol of the subframe 705 and asecond symbol of the subframe 705, a first CRS sequence 720, a secondCRS sequence 725, and control transmissions 730 may be transmitted. Inthis example, first CRS sequence 720 and a second CRS sequence 725 maybe concurrently transmitted using FDM in the first symbol, and controltransmissions 730 may be transmitted in the second symbol. A DMRS 735may be transmitted, followed by downlink data such as PDSCHtransmissions 740. In this example, within the first symbol of thesubframe 705 the first CRS sequence 720 occupies one-half of the symbol(e.g., every other frequency tone), with the remaining portion of thesymbol used for the second CRS sequence. Control transmissions 730 maybe in the second symbol of the subframe 705.

In examples where the UE has relatively poor channel quality, the firstCRS sequence 720 and second CRS sequence 725 may be used for controlchannel demodulation and burst detection. If a UE has relatively goodchannel quality, in some examples, only the first CRS sequence 720 (oronly the second CRS sequence 725) may be transmitted, with remainingportions of the first symbol containing control transmissions 730 in aconfiguration such as illustrated in FIG. 4. In such examples, a UE mayperform blind detection using two hypotheses to identify if just thefirst CRS sequence 720 is transmitted, or if a combined first CRSsequence 720 and second CRS sequence 725 are transmitted. Based on theoutcome of the blind detection, the UE may determine whether the firstsymbol includes control transmissions 730 and whether PDCCH starts withthe first symbol or the second symbol.

FIG. 8 shows a block diagram 800 of a device 805 that supports CRS andcontrol channel configuration in wireless communications in accordancewith various aspects of the present disclosure. Device 805 may be anexample of aspects of a base station 105 as described with reference toFIGS. 1-2. Device 805 may include receiver 810, base stationcommunications component 815, and transmitter 820. Device 805 may alsoinclude a processor. Each of these components may be in communicationwith one another (e.g., via one or more buses).

Receiver 810 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to CRS andcontrol channel configuration in wireless communications, etc.).Information may be passed on to other components of the device. Thereceiver 810 may be an example of aspects of the transceiver 1135described with reference to FIG. 11.

Base station communications component 815 may be an example of aspectsof the base station communications component 1115 described withreference to FIG. 11. Base station communications component 815 mayidentify at least a first UE that is to receive a downlink transmissionduring a first TTI, identify a channel quality of the first UE, andconfigure a CRS based on the channel quality of the first UE.

Transmitter 820 may transmit signals generated by other components ofthe device. In some examples, the transmitter 820 may be collocated witha receiver 810 in a transceiver module. For example, the transmitter 820may be an example of aspects of the transceiver 1135 described withreference to FIG. 11. The transmitter 820 may include a single antenna,or it may include a set of antennas. Transmitter 820 may transmit theCRS to the first UE during the first TTI and also transmit CRS to asecond UE during a second TTI.

FIG. 9 shows a block diagram 900 of a device 905 that supports CRS andcontrol channel configuration in wireless communications in accordancewith various aspects of the present disclosure. Device 905 may be anexample of aspects of a device 805 or a base station 105 as describedwith reference to FIGS. 1-2 and 8. Device 905 may include receiver 910,base station communications component 915, and transmitter 920. Device905 may also include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

Receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to CRS andcontrol channel configuration in wireless communications, etc.).Information may be passed on to other components of the device. Thereceiver 910 may be an example of aspects of the transceiver 1135described with reference to FIG. 11.

Base station communications component 915 may be an example of aspectsof the base station communications component 1115 described withreference to FIG. 11. Base station communications component 915 may alsoinclude UE identification component 925, channel quality component 930,and CRS component 935.

UE identification component 925 may identify at least a first UE that isto receive a downlink transmission during a first TTI and identify asecond UE that is to receive a downlink transmission during a secondTTI. Channel quality component 930 may identify a channel quality of thefirst UE and identify a channel quality of the second UE. Channelquality may be identified, in some examples, based on a CQI provided bythe UEs, a SRS received from the UEs, a RSRP of the UEs, a RSRQ of theUEs, or any combination thereof. CRS component 935 may configure a CRSfor the first TTI based on the channel quality of the first UE andconfigure a CRS for the second TTI based on the channel quality of thesecond UE.

Transmitter 920 may transmit signals generated by other components ofthe device. In some examples, the transmitter 920 may be collocated witha receiver 910 in a transceiver module. For example, the transmitter 920may be an example of aspects of the transceiver 1135 described withreference to FIG. 11. The transmitter 920 may include a single antenna,or it may include a set of antennas.

FIG. 10 shows a block diagram 1000 of a base station communicationscomponent 1015 that supports CRS and control channel configuration inwireless communications in accordance with various aspects of thepresent disclosure. The base station communications component 1015 maybe an example of aspects of a base station communications component 815,a base station communications component 915, or a base stationcommunications component 1115 described with reference to FIGS. 8, 9,and 11. The base station communications component 1015 may include UEidentification component 1020, Channel quality component 1025, CRScomponent 1030, control channel component 1035, CRS power component1040, CRS resource selection component 1045, and signaling component1050. Each of these modules may communicate, directly or indirectly,with one another (e.g., via one or more buses).

UE identification component 1020 may identify at least a first UE thatis to receive a downlink transmission during a first TTI and identify asecond UE that is to receive a downlink transmission during a secondTTI. Channel quality component 1025 may identify a channel quality ofthe first UE and identify a channel quality of the second UE. Channelquality may be identified, in some examples, based on a CQI provided bythe UEs, a SRS received from the UEs, a RSRP of the UEs, a RSRQ of theUEs, or any combination thereof. CRS component 1030 may configure a CRSfor the first TTI based on the channel quality of the first UE andconfigure a CRS for the second TTI based on the channel quality of thesecond UE.

Control channel component 1035 may configure a starting point for adownlink control channel transmission to the first UE within the TTIbased on the CRS for the TTI. In some examples, a subset of REs of asymbol of a TTI may be configured for CRS, and a second subset of theREs may be configured for downlink control channel transmission. Thecontrol channel component 1035 may configure a concurrent downlinkcontrol channel transmission and CRS transmission in different subsetsof resources of the first symbol when the channel quality of the firstUE exceeds a threshold value. In some cases, the downlink controlchannel transmission is deferred to a second symbol of the TTI after thefirst symbol when a second power for the second subset of REs is below apower threshold value. In some cases, the CRS and control channelconfiguration may be dynamically configured for each TTI of a pluralityof TTIs based at least in part on the channel quality of one or more UEsto receive the downlink transmission during the TTI.

CRS power component 1040 may configure CRS transmission power based onthe channel quality of the first UE, and configure a concurrent downlinkcontrol channel transmission power based on the CRS transmission power.In some cases, in a first symbol, a first power for a first subset ofREs may be configured based on the channel quality of the first UE, anda second power for a second subset of REs configured based on the firstpower. In some cases, the first power for the first subset of REs isconfigured with a higher power than the second power for the secondsubset of REs when the channel quality of the first UE is below athreshold value. In some cases, the first power for the first subset ofREs is configured with equivalent power as the second power for thesecond subset of REs when the channel quality of the first UE is above athreshold value.

CRS resource selection component 1045 may select CRS resources fortransmissions to a UE. In some cases, two sets of CRS resources may beprovided, and the CRS resource selection component 1045 may configure afirst CRS for transmission in a first subset of resources of a firstsymbol, and may configure a second CRS for transmission in a secondsubset of resources of the first symbol when the channel quality of thefirst UE does not exceed the threshold value. In some cases, each of afirst symbol of the TTI and a second symbol of the TTI include a set ofresource elements (REs), and where the configuring the CRS includes:configuring a first subset of the REs across the first symbol and secondsymbol for transmission of the CRS. In some cases, the configuring theCRS includes configuring a first CRS for transmission in a first subsetof resources of a first symbol of the TTI based on the channel qualityof the first UE. In some cases, the configuring the CRS further includesdetermining whether the channel quality of the first UE exceeds athreshold value.

Signaling component 1050 may transmit signaling to the first UE thatindicates whether the PDCCH transmission starts in the first symbol orin the second symbol based on the channel quality of the UE. In somecases, signaling component 1050 may transmit signaling to the first UEthat the first UE is to receive the CRS transmitted in the first symbolor that the first UE is to combine the CRS transmissions from the firstsymbol and the second symbol. In some cases, the signaling includes L1signaling transmitted in the first symbol or a search space restrictionfor the first UE.

FIG. 11 shows a diagram of a system 1100 including a device 1105 thatsupports CRS and control channel configuration in wirelesscommunications in accordance with various aspects of the presentdisclosure. Device 1105 may be an example of or include the componentsof device 805, device 905, or a base station 105 as described above,e.g., with reference to FIGS. 1, 8 and 9. Device 1105 may includecomponents for bi-directional voice and data communications includingcomponents for transmitting and receiving communications, including basestation communications component 1115, processor 1120, memory 1125,software 1130, transceiver 1135, antenna 1140, network communicationsmanager 1145, and base station communications manager 1150. Thesecomponents may be in electronic communication via one or more busses(e.g., bus 1110). Device 1105 may communicate wirelessly with one ormore UEs 115. Base station communications component 1115 may be anexample of aspects of the base station communications componentdescribed with reference to FIGS. 1-2 and 8-10.

Processor 1120 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a digital signal processor (DSP), a centralprocessing unit (CPU), a microcontroller, an application-specificintegrated circuit (ASIC), an field-programmable gate array (FPGA), aprogrammable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, processor 1120 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into processor 1120. Processor 1120 may be configured toexecute computer-readable instructions stored in a memory to performvarious functions (e.g., functions or tasks supporting CRS and controlchannel configuration in wireless communications).

Memory 1125 may include random access memory (RAM) and read only memory(ROM). The memory 1125 may store computer-readable, computer-executablesoftware 1130 including instructions that, when executed, cause theprocessor to perform various functions described herein. In some cases,the memory 1125 may contain, among other things, a basic input/outputsystem (BIOS) which may control basic hardware and/or software operationsuch as the interaction with peripheral components or devices.

Software 1130 may include code to implement aspects of the presentdisclosure, including code to support CRS and control channelconfiguration in wireless communications. Software 1130 may be stored ina non-transitory computer-readable medium such as system memory or othermemory. In some cases, the software 1130 may not be directly executableby the processor but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

Transceiver 1135 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1135 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1135 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1140.However, in some cases the device may have more than one antenna 1140,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

Network communications manager 1145 may manage communications with thecore network (e.g., via one or more wired backhaul links). For example,the network communications manager 1145 may manage the transfer of datacommunications for client devices, such as one or more UEs 115.

Base station communications manager 1150 may manage communications withother base station 105, and may include a controller or scheduler forcontrolling communications with UEs 115 in cooperation with other basestations 105. For example, the base station communications manager 1150may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, base station communications manager 1150may provide an X2 interface within an Long Term Evolution (LTE)/LTE-Awireless communication network technology to provide communicationbetween base stations 105.

FIG. 12 shows a block diagram 1200 of a device 1205 that supports CRSand control channel configuration in wireless communications inaccordance with various aspects of the present disclosure. Device 1205may be an example of aspects of a UE 115 as described with reference toFIGS. 1-2. Device 1205 may include receiver 1210, UE communicationscomponent 1215, and transmitter 1220. Device 1205 may also include aprocessor. Each of these components may be in communication with oneanother (e.g., via one or more buses).

Receiver 1210 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to CRS andcontrol channel configuration in wireless communications, etc.).Information may be passed on to other components of the device. Thereceiver 1210 may be an example of aspects of the transceiver 1535described with reference to FIG. 15. Receiver 1210 may receive, at a UE,a downlink transmission from a base station during a first TTI.

UE communications component 1215 may be an example of aspects of the UEcommunications component 1515 described with reference to FIG. 15. UEcommunications component 1215 may determine a CRS configuration of thedownlink transmission and receive the CRS based on the CRSconfiguration.

Transmitter 1220 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1220 may be collocatedwith a receiver 1210 in a transceiver module. For example, thetransmitter 1220 may be an example of aspects of the transceiver 1535described with reference to FIG. 15. The transmitter 1220 may include asingle antenna, or it may include a set of antennas.

FIG. 13 shows a block diagram 1300 of a device 1305 that supports CRSand control channel configuration in wireless communications inaccordance with various aspects of the present disclosure. Device 1305may be an example of aspects of a device 1205 or a UE 115 as describedwith reference to FIGS. 1 and 12. Device 1305 may include receiver 1310,UE communications component 1315, and transmitter 1320. Device 1305 mayalso include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

Receiver 1310 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to CRS andcontrol channel configuration in wireless communications, etc.).Information may be passed on to other components of the device. Thereceiver 1310 may be an example of aspects of the transceiver 1535described with reference to FIG. 15.

UE communications component 1315 may be an example of aspects of the UEcommunications component 1515 described with reference to FIG. 15. UEcommunications component 1315 may also include CRS resourceidentification component 1325 and CRS component 1330.

CRS resource identification component 1325 may determine a CRSconfiguration of the downlink transmission, receive signaling from thebase station that indicates whether only a first symbol of the TTI orboth the first symbol and a second symbol of the TTI include CRS anddownlink control information, and, when both the first symbol and thesecond symbol include CRS and downlink control information, whether thesecond symbol includes CRS transmissions. In some cases, CRS resourceidentification component 1325 may determine the CRS configuration byblindly detecting the presence of a first or a second CRS sequence. Insome cases, the determining the CRS configuration includes determiningthat a first CRS is configured for transmission in a first subset ofresources of a first symbol of the TTI.

CRS component 1330 may receive the CRS based on the CRS configuration.In some cases, each of a first symbol of the TTI and a second symbol ofthe TTI include a portion of the CRS transmission, and where thereceiving the CRS includes: combining CRS transmissions received in thefirst symbol and second symbol.

Transmitter 1320 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1320 may be collocatedwith a receiver 1310 in a transceiver module. For example, thetransmitter 1320 may be an example of aspects of the transceiver 1535described with reference to FIG. 15. The transmitter 1320 may include asingle antenna, or it may include a set of antennas.

FIG. 14 shows a block diagram 1400 of a UE communications component 1415that supports CRS and control channel configuration in wirelesscommunications in accordance with various aspects of the presentdisclosure. The UE communications component 1415 may be an example ofaspects of a UE communications component 1515 described with referenceto FIGS. 12, 13, and 15. The UE communications component 1415 mayinclude CRS resource identification component 1420, CRS component 1425,control channel component 1430, and signaling component 1435. Each ofthese modules may communicate, directly or indirectly, with one another(e.g., via one or more buses).

CRS resource identification component 1420 may determine a CRSconfiguration of the downlink transmission, and receive signaling fromthe base station that indicates whether only a first symbol of the TTIor both the first symbol and a second symbol of the TTI include CRS anddownlink control information. In some cases, when both the first symboland the second symbol include CRS and downlink control information, theCRS resource identification component 1420 may determine whether thesecond symbol includes CRS transmissions. In some cases, the CRSresource identification component 1420 may blindly detect the presenceof a first CRS sequence or a second CRS sequence.

CRS component 1425 may receive the CRS based on the CRS configuration.In some cases, each of a first symbol of the TTI and a second symbol ofthe TTI include a portion of the CRS transmission, and the receiving theCRS includes combining CRS transmissions received in the first symboland second symbol. Control channel component 1430 may determine astarting point for a downlink control channel transmission within theTTI based on the CRS configuration.

Signaling component 1435 may receive signaling that indicates a startingpoint for a PDCCH based on the CRS configuration and receive signalingthat the CRS transmissions from the first symbol and the second symbolare to be combined. In some cases, the signaling includes L1 signalingtransmitted in a first symbol of the TTI or a search space restrictionfor the first UE.

FIG. 15 shows a diagram of a system 1500 including a device 1505 thatsupports CRS and control channel configuration in wirelesscommunications in accordance with various aspects of the presentdisclosure. Device 1505 may be an example of or include the componentsof UE 115 as described above, e.g., with reference to FIG. 1. Device1505 may include components for bi-directional voice and datacommunications including components for transmitting and receivingcommunications, including UE communications component 1515, processor1520, memory 1525, software 1530, transceiver 1535, antenna 1540, andI/O controller 1545. These components may be in electronic communicationvia one or more busses (e.g., bus 1510). Device 1505 may communicatewirelessly with one or more base stations 105. UE communicationscomponent 1515 may be an example of aspects of the UE communicationscomponent described with reference to FIGS. 1-2 and 12-14.

Processor 1520 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, processor 1520 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into processor 1520. Processor 1520 may be configured toexecute computer-readable instructions stored in a memory to performvarious functions (e.g., functions or tasks supporting CRS and controlchannel configuration in wireless communications).

Memory 1525 may include RAM and ROM. The memory 1525 may storecomputer-readable, computer-executable software 1530 includinginstructions that, when executed, cause the processor to perform variousfunctions described herein. In some cases, the memory 1525 may contain,among other things, a BIOS which may control basic hardware and/orsoftware operation such as the interaction with peripheral components ordevices.

Software 1530 may include code to implement aspects of the presentdisclosure, including code to support CRS and control channelconfiguration in wireless communications. Software 1530 may be stored ina non-transitory computer-readable medium such as system memory or othermemory. In some cases, the software 1530 may not be directly executableby the processor but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

Transceiver 1535 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1535 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1535 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1540.However, in some cases the device may have more than one antenna 1540,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

I/O controller 1545 may manage input and output signals for device 1505.I/O controller 1545 may also manage peripherals not integrated intodevice 1505. In some cases, I/O controller 1545 may represent a physicalconnection or port to an external peripheral. In some cases, I/Ocontroller 1545 may utilize an operating system such as iOS®, ANDROID®,MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operatingsystem.

FIG. 16 shows a flowchart illustrating a method 1600 for CRS and controlchannel configuration in wireless communications in accordance withvarious aspects of the present disclosure. The operations of method 1600may be implemented by a base station 105 or its components as describedherein. For example, the operations of method 1600 may be performed by abase station communications component as described with reference toFIGS. 8 through 11. In some examples, a base station 105 may execute aset of codes to control the functional elements of the device to performthe functions described below. Additionally or alternatively, the basestation 105 may perform aspects the functions described below usingspecial-purpose hardware.

At block 1605 the base station 105 may identify at least a first UE thatis to receive a downlink transmission during a first TTI. The operationsof block 1605 may be performed according to the methods described withreference to FIGS. 1 through 7. In certain examples, aspects of theoperations of block 1605 may be performed by a UE identificationcomponent as described with reference to FIGS. 8 through 11.

At block 1610 the base station 105 may identify a channel quality of thefirst UE. The operations of block 1610 may be performed according to themethods described with reference to FIGS. 1 through 7. In certainexamples, aspects of the operations of block 1610 may be performed by achannel quality component as described with reference to FIGS. 8 through11.

At block 1615 the base station 105 may configure a CRS based at least inpart on the channel quality of the first UE. The operations of block1615 may be performed according to the methods described with referenceto FIGS. 1 through 7. In certain examples, aspects of the operations ofblock 1615 may be performed by a CRS component as described withreference to FIGS. 8 through 11.

At block 1620 the base station 105 may configure a starting point for adownlink control channel transmission to the first UE within the TTIbased on the CRS. The operations of block 1620 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 1620 may beperformed by a control channel component as described with reference toFIGS. 8 through 11.

At block 1625 the base station 105 may transmit the CRS to the first UEduring the first TTI. The operations of block 1625 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 1625 may beperformed by a transmitter as described with reference to FIGS. 8through 11. In some examples, the transmission may include an indicationof a starting point within the TTI (e.g., within a first symbol orwithin a second symbol) for the control channel transmission. Such atransmission may include an indication, for example, in L1 signalingwithin the first symbol that may be received by the first UE and used todetermine where the control channel transmission begins.

FIG. 17 shows a flowchart illustrating a method 1700 for CRS and controlchannel configuration in wireless communications in accordance withvarious aspects of the present disclosure. The operations of method 1700may be implemented by a base station 105 or its components as describedherein. For example, the operations of method 1700 may be performed by abase station communications component as described with reference toFIGS. 8 through 11. In some examples, a base station 105 may execute aset of codes to control the functional elements of the device to performthe functions described below. Additionally or alternatively, the basestation 105 may perform aspects the functions described below usingspecial-purpose hardware.

At block 1705 the base station 105 may identify at least a first UE thatis to receive a downlink transmission during a first TTI. The operationsof block 1705 may be performed according to the methods described withreference to FIGS. 1 through 7. In certain examples, aspects of theoperations of block 1705 may be performed by a UE identificationcomponent as described with reference to FIGS. 8 through 11.

At block 1710 the base station 105 may identify a channel quality of thefirst UE. The operations of block 1710 may be performed according to themethods described with reference to FIGS. 1 through 7. In certainexamples, aspects of the operations of block 1710 may be performed by achannel quality component as described with reference to FIGS. 8 through11.

At block 1715 the base station 105 may configure a CRS based at least inpart on the channel quality of the first UE. The operations of block1715 may be performed according to the methods described with referenceto FIGS. 1 through 7. In certain examples, aspects of the operations ofblock 1715 may be performed by a CRS component as described withreference to FIGS. 8 through 11.

At block 1720 the base station 105 may transmit the CRS to the first UEduring the first TTI. The operations of block 1720 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 1720 may beperformed by a transmitter as described with reference to FIGS. 8through 11.

At block 1725 the base station 105 may identify a second UE that is toreceive a downlink transmission during a second TTI. The operations ofblock 1725 may be performed according to the methods described withreference to FIGS. 1 through 7. In certain examples, aspects of theoperations of block 1725 may be performed by a UE identificationcomponent as described with reference to FIGS. 8 through 11.

At block 1730 the base station 105 may identify a channel quality of thesecond UE. The operations of block 1730 may be performed according tothe methods described with reference to FIGS. 1 through 7. In certainexamples, aspects of the operations of block 1730 may be performed by achannel quality component as described with reference to FIGS. 8 through11.

At block 1735 the base station 105 may configure a CRS based at least inpart on the channel quality of the second UE. The operations of block1735 may be performed according to the methods described with referenceto FIGS. 1 through 7. In certain examples, aspects of the operations ofblock 1735 may be performed by a CRS component as described withreference to FIGS. 8 through 11.

At block 1740 the base station 105 may transmit the CRS to the second UEduring the second TTI. The operations of block 1740 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 1740 may beperformed by a transmitter as described with reference to FIGS. 8through 11.

FIG. 18 shows a flowchart illustrating a method 1800 for CRS and controlchannel configuration in wireless communications in accordance withvarious aspects of the present disclosure. The operations of method 1800may be implemented by a base station 105 or its components as describedherein. For example, the operations of method 1800 may be performed by abase station communications component as described with reference toFIGS. 8 through 11. In some examples, a base station 105 may execute aset of codes to control the functional elements of the device to performthe functions described below. Additionally or alternatively, the basestation 105 may perform aspects the functions described below usingspecial-purpose hardware.

At block 1805 the base station 105 may identify at least a first UE thatis to receive a downlink transmission during a first TTI. The operationsof block 1805 may be performed according to the methods described withreference to FIGS. 1 through 7. In certain examples, aspects of theoperations of block 1805 may be performed by a UE identificationcomponent as described with reference to FIGS. 8 through 11.

At block 1810 the base station 105 may identify a channel quality of thefirst UE. The operations of block 1810 may be performed according to themethods described with reference to FIGS. 1 through 7. In certainexamples, aspects of the operations of block 1810 may be performed by achannel quality component as described with reference to FIGS. 8 through11.

At block 1815 the base station 105 may configure a CRS based at least inpart on the channel quality of the first UE. The operations of block1815 may be performed according to the methods described with referenceto FIGS. 1 through 7. In certain examples, aspects of the operations ofblock 1815 may be performed by a CRS component as described withreference to FIGS. 8 through 11.

At block 1820 the base station 105 may transmit the CRS to the first UEduring the first TTI. The operations of block 1820 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 1820 may beperformed by a transmitter as described with reference to FIGS. 8through 11.

At block 1825 the base station 105 may transmit, based at least in parton the channel quality of the first UE, signaling to the first UE thatindicates whether only a first symbol of the TTI or both the firstsymbol and a second symbol of the TTI include CRS and downlink controlinformation, and, when both the first symbol and the second symbolinclude CRS and downlink control information, whether the second symbolincludes CRS transmissions. The operations of block 1825 may beperformed according to the methods described with reference to FIGS. 1through 7. In certain examples, aspects of the operations of block 1825may be performed by a signaling component as described with reference toFIGS. 8 through 11.

FIG. 19 shows a flowchart illustrating a method 1900 for CRS and controlchannel configuration in wireless communications in accordance withvarious aspects of the present disclosure. The operations of method 1900may be implemented by a UE 115 or its components as described herein.For example, the operations of method 1900 may be performed by a UEcommunications component as described with reference to FIGS. 12 through15. In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware.

At block 1905 the UE 115 may receive, at a user equipment (UE), adownlink transmission from a base station during a first TTI. Theoperations of block 1905 may be performed according to the methodsdescribed with reference to FIGS. 1 through 7. In certain examples,aspects of the operations of block 1905 may be performed by a receiveras described with reference to FIGS. 12 through 15.

At block 1910 the UE 115 may determine a CRS configuration of thedownlink transmission. The operations of block 1910 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 1910 may beperformed by a CRS resource identification component as described withreference to FIGS. 12 through 15.

At block 1915 the UE 115 may receive the CRS based at least in part onthe CRS configuration. The operations of block 1915 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 1915 may beperformed by a CRS component as described with reference to FIGS. 12through 15. In some examples, the UE 115 may also receive an indicationof a starting point within the first TTI (e.g., within a first symbol ofthe first TTI or within a second symbol of the first TTI) for a controlchannel transmission. Such an indication may be received, for example,in L1 signaling within the first symbol and used to determine where thecontrol channel transmission begins.

FIG. 20 shows a flowchart illustrating a method 2000 for CRS and controlchannel configuration in wireless communications in accordance withvarious aspects of the present disclosure. The operations of method 2000may be implemented by a UE 115 or its components as described herein.For example, the operations of method 2000 may be performed by a UEcommunications component as described with reference to FIGS. 12 through15. In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware.

At block 2005 the UE 115 may receive a downlink transmission from a basestation during a first TTI. The operations of block 2005 may beperformed according to the methods described with reference to FIGS. 1through 7. In certain examples, aspects of the operations of block 2005may be performed by a receiver as described with reference to FIGS. 12through 15.

At block 2010 the UE 115 may determine a CRS configuration of thedownlink transmission. The operations of block 2010 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 2010 may beperformed by a CRS resource identification component as described withreference to FIGS. 12 through 15.

At block 2015 the UE 115 may receive the CRS based at least in part onthe CRS configuration. The operations of block 2015 may be performedaccording to the methods described with reference to FIGS. 1 through 7.In certain examples, aspects of the operations of block 2015 may beperformed by a CRS component as described with reference to FIGS. 12through 15.

At block 2020 the UE 115 may receive signaling from the base stationthat indicates whether only a first symbol of the TTI or both the firstsymbol and a second symbol of the TTI include CRS and downlink controlinformation, and, when both the first symbol and the second symbolinclude CRS and downlink control information, whether the second symbolincludes CRS transmissions. The operations of block 2020 may beperformed according to the methods described with reference to FIGS. 1through 7. In certain examples, aspects of the operations of block 2020may be performed by a CRS resource identification component as describedwith reference to FIGS. 12 through 15.

It should be noted that the methods described above describe possibleimplementations, and that the operations may be rearranged or otherwisemodified and that other implementations are possible. Furthermore,aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.The terms “system” and “network” are often used interchangeably. A codedivision multiple access (CDMA) system may implement a radio technologysuch as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc.CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releasesmay be commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. Atime division multiple access (TDMA) system may implement a radiotechnology such as Global System for Mobile Communications (GSM).

An orthogonal frequency division multiple access (OFDMA) system mayimplement a radio technology such as Ultra Mobile Broadband (UMB),Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM,etc. UTRA and E-UTRA are part of Universal Mobile Telecommunicationssystem (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A)are releases of Universal Mobile Telecommunications System (UMTS) thatuse E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and Global System for Mobilecommunications (GSM) are described in documents from the organizationnamed “3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the systems and radio technologies mentioned above as well asother systems and radio technologies. While aspects an LTE system may bedescribed for purposes of example, and LTE terminology may be used inmuch of the description, the techniques described herein are applicablebeyond LTE applications.

In LTE/LTE-A networks, including such networks described herein, theterm evolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-A network in which different typesof evolved node B (eNBs) provide coverage for various geographicalregions. For example, each eNB or base station may provide communicationcoverage for a macro cell, a small cell, or other types of cell. Theterm “cell” may be used to describe a base station, a carrier orcomponent carrier associated with a base station, or a coverage area(e.g., sector, etc.) of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an accesspoint, a radio transceiver, a NodeB, eNodeB (eNB), gNodeB (gNB) HomeNodeB, a Home eNodeB, or some other suitable terminology. The geographiccoverage area for a base station may be divided into sectors making uponly a portion of the coverage area. The wireless communications systemor systems described herein may include base stations of different types(e.g., macro or small cell base stations). The UEs described herein maybe able to communicate with various types of base stations and networkequipment including macro eNBs, small cell eNBs, relay base stations,and the like. There may be overlapping geographic coverage areas fordifferent technologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base station, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers). A UE may be able to communicate with varioustypes of base stations and network equipment including macro eNBs, smallcell eNBs, relay base stations, and the like.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The downlink transmissions described herein may also be called forwardlink transmissions while the uplink transmissions may also be calledreverse link transmissions. Each communication link describedherein—including, for example, wireless communications system 100 and200 of FIGS. 1 and 2—may include one or more carriers, where eachcarrier may be a signal made up of multiple sub-carriers (e.g., waveformsignals of different frequencies).

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of at least one of A, B, or C meansA or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, asused herein, the phrase “based on” shall not be construed as a referenceto a closed set of conditions. For example, an exemplary operation thatis described as “based on condition A” may be based on both a conditionA and a condition B without departing from the scope of the presentdisclosure. In other words, as used herein, the phrase “based on” shallbe construed in the same manner as the phrase “based at least in parton.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media maycomprise RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave are included in the definition of medium. Disk and disc,as used herein, include CD, laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication, comprising:identifying at least a first user equipment (UE) that is to receive adownlink transmission during a first transmission time interval (TTI);identifying a channel quality of the first UE; configuring acell-specific reference signal (CRS) based at least in part on thechannel quality of the first UE; and transmitting the CRS to the firstUE during the first TTI.
 2. The method of claim 1, wherein theconfiguring the CRS comprises: dynamically configuring the CRS for eachTTI of a plurality of TTIs based at least in part on a channel qualityof one or more UEs to receive the downlink transmission during the TTI.3. The method of claim 1, further comprising: configuring a startingpoint for a downlink control channel transmission to the first UE withinthe TTI based at least in part on the CRS.
 4. The method of claim 1,wherein configuring the CRS comprises: configuring a CRS transmissionpower based at least in part on the channel quality of the first UE; andconfiguring a concurrent downlink control channel transmission powerbased at least in part on the CRS transmission power.
 5. The method ofclaim 1, further comprising: identifying a second set of UEs that are toreceive a second downlink transmission during a second TTI; identifyinga second UE of the second set of UEs having a poorer channel qualitythan other UEs of the second set of UEs; configuring a second CRS basedat least in part on the channel quality of the second UE; andtransmitting the second CRS to the second set of UEs during the secondTTI.
 6. The method of claim 1, wherein a first symbol of the TTIcomprises a set of resource elements (REs), and wherein the configuringthe CRS comprises: configuring a first subset of the REs fortransmission of the CRS; configuring a second subset of the REs for adownlink control channel transmission; configuring a first power for thefirst subset of the REs based at least in part on the channel quality ofthe first UE; and configuring a second power for the second subset ofthe REs based at least in part on the first power.
 7. The method ofclaim 6, wherein a second symbol of the TTI comprises a physicaldownlink control channel (PDCCH) transmission.
 8. The method of claim 7,further comprising: transmitting signaling to the first UE thatindicates whether the PDCCH transmission starts in the first symbol orin the second symbol.
 9. The method of claim 6, wherein the first powerfor the first subset of the REs is configured with a higher power thanthe second power for the second subset of the REs when the channelquality of the first UE is below a threshold value.
 10. The method ofclaim 9, wherein the downlink control channel transmission is deferredto a second symbol of the TTI after the first symbol when the secondpower for the second subset of the REs is below a power threshold value.11. The method of claim 9, wherein the first power for the first subsetof the REs is configured with equivalent power as the second power forthe second subset of the REs when the channel quality of the first UE isabove a threshold value.
 12. The method of claim 1, wherein each of afirst symbol of the TTI and a second symbol of the TTI comprise a set ofresource elements (REs), and wherein the configuring the CRS comprises:configuring a first subset of the REs across the first symbol and secondsymbol for transmission of the CRS; configuring a second subset of theREs in each of the first symbol and second symbol for transmission of adownlink control channel transmission.
 13. The method of claim 12,further comprising: transmitting signaling to the first UE that thefirst UE is to receive the CRS transmitted in the first symbol or thatthe first UE is to combine CRS transmissions from the first symbol andthe second symbol, based at least in part on the channel quality of thefirst UE.
 14. The method of claim 1, further comprising: transmitting,based at least in part on the channel quality of the first UE, signalingto the first UE that indicates whether only a first symbol of the TTI orboth the first symbol and a second symbol of the TTI include CRS anddownlink control information, and, when both the first symbol and thesecond symbol include CRS and downlink control information, whether thesecond symbol includes CRS transmissions.
 15. The method of claim 1,wherein the configuring the CRS comprises: configuring a first CRS fortransmission in a first subset of resources of a first symbol of the TTIbased at least in part on the channel quality of the first UE.
 16. Themethod of claim 15, wherein the configuring the CRS further comprises:determining whether the channel quality of the first UE exceeds athreshold value; configuring a concurrent downlink control channeltransmission in a second subset of resources of the first symbol whenthe channel quality of the first UE exceeds the threshold value; andconfiguring a second CRS for transmission in the second subset ofresources of the first symbol when the channel quality of the first UEdoes not exceed the threshold value.
 17. A method for wirelesscommunication, comprising: receiving, at a user equipment (UE), adownlink transmission from a base station during a first transmissiontime interval (TTI); determining a cell-specific reference signal (CRS)configuration of the downlink transmission, the CRS configuration basedat least in part on a channel quality of the first UE during the firstTTI; and receiving the CRS based at least in part on the CRSconfiguration.
 18. The method of claim 17, further comprising:determining a starting point for a downlink control channel transmissionwithin the TTI based at least in part on the CRS configuration.
 19. Themethod of claim 17, further comprising: receiving signaling thatindicates a starting point for a physical downlink control channel(PDCCH) transmission within the first TTI.
 20. The method of claim 19,wherein the signaling comprises layer-one (L1) signaling transmitted ina first symbol of the TTI or a search space restriction for the firstUE.
 21. The method of claim 19, wherein each of a first symbol of theTTI and a second symbol of the TTI comprise a portion of the CRS, andwherein the receiving the CRS comprises: combining CRS transmissionsreceived in the first symbol and second symbol.
 22. The method of claim21, further comprising: receiving signaling that the CRS transmissionsfrom the first symbol and the second symbol are to be combined.
 23. Themethod of claim 17, further comprising: receiving signaling from thebase station that indicates whether only a first symbol of the TTI orboth the first symbol and a second symbol of the TTI include CRS anddownlink control information, and, when both the first symbol and thesecond symbol include CRS and downlink control information, whether thesecond symbol includes CRS transmissions.
 24. The method of claim 17,wherein the determining the CRS configuration comprises: determiningthat a first CRS is configured for transmission in a first subset ofresources of a first symbol of the TTI; and determining whether aconcurrent downlink control channel transmission is configured in asecond subset of resources of the first symbol or a second CRS isconfigured for transmission in the second subset of resources of thefirst symbol.
 25. The method of claim 24, wherein determining the CRSconfiguration comprises blindly detecting a presence of the second CRS.26. An apparatus for wireless communication, comprising: a processor;memory in electronic communication with the processor; and the processorand memory configured to: identify at least a first user equipment (UE)that is to receive a downlink transmission during a first transmissiontime interval (TTI); identify a channel quality of the first UE;configure a cell-specific reference signal (CRS) based at least in parton the channel quality of the first UE; and transmit the CRS to thefirst UE during the first TTI.
 27. The apparatus of claim 26, whereinthe processor and memory are further configured to: identify a secondset of UEs that are to receive a second downlink transmission during asecond TTI; identify a second UE of the second set of UEs having apoorer channel quality than other UEs of the second set of UEs;configure a second CRS based at least in part on the channel quality ofthe second UE; and transmit the second CRS to the second set of UEsduring the second TTI.
 28. The apparatus of claim 26, wherein a firstsymbol of the TTI comprises a set of resource elements (REs), andwherein the processor and memory are further configured to: configure afirst subset of the REs for transmission of the CRS; configure a secondsubset of the REs for a downlink control channel transmission; configurea first power for the first subset of the REs based at least in part onthe channel quality of the first UE; and configure a second power forthe second subset of the REs based at least in part on the first power.29. An user equipment (UE) apparatus for wireless communication,comprising: a processor; memory in electronic communication with theprocessor; and the processor and memory configured to: receive adownlink transmission from a base station during a first transmissiontime interval (TTI); determine a cell-specific reference signal (CRS)configuration of the downlink transmission, the CRS configuration basedat least in part on a channel quality of the UE during the first TTI;and receive the CRS based at least in part on the CRS configuration. 30.The apparatus of claim 29, wherein the processor and memory are furtherconfigured to: determine a starting point for a downlink control channeltransmission within the TTI based at least in part on the CRSconfiguration.